Search on ec_user_session_info in www/admin/ecommerce/customer-service/spam-2.tcl and www/admin/ecommerce/customer-service/spam-3.tcl. It looks like the information is used to spam users who have recently viewed a product or category. The fact that you can't delete a product or category seems like a design oversight. Since you only need the ec_user_session_info for creating ecommerce spam, you should be able a add triggers to delete the corresponding entries from the ec_user_session_info table when deleting a product or category.
